High-dose chemotherapy is potentially curative in some chemosensitive tumors and a relationship between dose intensity and cytotoxic drugs and tumor response has been defined for several malignancies. The applicable dose of chemical agents used for the treatment of cancer is mostly limited by myeloid suppression, as well as non-haematological organ toxicity. The risk of neutropenic infection and of bleeding complications requires expensive supportive care during this period. Since, however, by an intensive treatment the probability of destroying most of the committed progenitor cells is high, generally high doses of chemotherapeutic active agents are administered.
It is therefore one object of the present invention to overcome the problems associated with high-dose chemotherapy by providing a process for the ex vivo expansion of peripheral blood progenitor cells which can be administered to patients after high-dose chemotherapy.
In their publication "Engraftment After Infusion of CD 34.sup.+ Marrow Cells in Patients With Breast Cancer or Neuroblastoma" (Blood, Vol. 77, No. 8 (1991), pp. 1717-1722) Berenson et al. have described the CD 34 antigen. The CD 34 antigen is expressed by 1% to 4% of human marrow cells. Because the CD 34 antigen has not been detected on most solid tumors, a positive selection of cells expressing the CD 34 antigen may be used to provide marrow cells capable of engraftment, but depleted of tumor cells.